Telegraph system



July 30, 1929. J. A. EYSTER TELEGRAPH SYSTEM File y 2 1928 2 Sheets-Sheet 1 INVENTOR JEE/yster BY ATTORNEY July 30, 1929. J. A. EYSTER TELEGRAPH SYSTEM Filed May 24, 1928 2 Sheets-Sheet 2/ muh 1% III] INVENTOR BY JAZZ 5621 ATTORNEY Patented July 3%, 1929..

pause earn JAMES A. EYSTEE, RIVER EDGE, NEW JERSEY, ASSIGNOR T0 AMERICAN TELE- PHONE AND TELEGRAPH COMPANY, A CORPORATION OF NEW YORK.

TELEGRAPH SYSTEM.-

Application filed Ma 24,

This invention relates to telegraph systems, and more particularly to improvements in telegraph line terminal circuits for automatically maintaining a constant direction 5 of current flow in the subscribers loop regardless of the direction of current supplied to it at the central office.

The reversal of direction of current flow in a telegraph subscribers loop is often objec-- 1O tionable, particularly in instances wherein printing telegraph equipment is included in the loop circuit. This may be due to the fact that the printing telegraph equipment may include polar relay apparatus and, therefore,

the reversal of the loop current would leave the printer in the spacing condition, or in a condition unresponsive to signals. Other types of apparatus in a subscribers loop dependent in operation upon current of a certain polarity would obviously be adversely affected by a reversal in the direction of the loop current.

In the arrangementsof this invention, re-

lay means are provided associated with the telegraph line terminal which, in response to a reversal of direction of the current in the loop circuit, will autmatically reverse the loop circuit connections at the central oflice so that the direction of current flow therethrough f will be the same as previously. The utilization of the arrangements of the invention will eliminate the present necessity of the subscribers informing the repeater Jattendant when the loop circuit has been set up with an improper connection so that the polarity of the current is wrong. The arrangements of the invention will also eliminate the necessity forthe repeater attendant to determine which is the proper polarity for the loop current as has been found necessary in setting up two terminal repeaters to act asan intermediate repeater with loops. The arrange ments of the invention will furthermore prevent the possibility of signals being sent for 'a period of time from the central office while the subscribers apparatus is in a condition unresponsive thereto. Other objects and features of the invention will appear more fully from the detailed description thereofhereinafter given. I

The invention may be more fully understood from the following description, together with the accompanying drawing in 1928. Serial No. 280,259.

the Figures 1, 2, 3, 4 and 5 of which the invention is illustrated. Similar reference characters have been utilized to denote like 7 parts in all of the figures.

In Fig. 1 is shown a section 1 of a telegraph line terminating at a central oflice and controlling the receiving relay 2. The spacing and marking contacts of the receiving relay are shown associated with the sources of curi rent of opposite polarity 3 and 4:. A break relay 5 and a sending relay 6 are shown. The sending relay 6 controls a short circuit 7 to '65 be closed across the output of the oscillator of carrier frequency utilized for sending. This apparatus is not shown. A' key 8 may be included in the circuit. As the above described apparatus is well known in the art, no further description thereof will be given.

The telegraph line terminal apparatus includes a number of jacks of which the jacks 12 and 15 are illustrated. Associated with the line at the central office are the relays 9 7 and 10. Relay?) is a' difierential relay with one circuit closing contactwhich controls the relay 10. Relay 10 is a single winding relay with two transfer contacts. One of the windings of the differential relay 9 is included in series in the loop circuit. The other winding of relay 9 acts as a polarizingwinding and is energized continuously by an outside source of potential, such as battery 21. The contacts of relay 10 are connected into both sides of '85 the loop circuit in such a way as to reverse its polarity when the relay 10 operates. The loop circuit will also include a battery 18 and apparatus 14. at a subscribers station. The apparatus 1 may, for example, be printing 9o telegraph apparatus including polar relays or the apparatus 14 may be any apparatus depending for its operation upon current of a certain polarity in the loop circuit. It is obvious that iffor any reason the polarity of 95. battery 18 should be reversed, the apparatus 14 would not function properly.

The operating, holding and releasing values of the circuits for relay?) are so chosen that the arrangements will operate 'as 'fo'llows. With normal current in the loop in the normal direction,'the effects of the two i windings of the differential relay 9 will'neutralize each other and the relay 9 will'remain normal and unoperated. The relay 10 will 1 also remain normal'and the direction ofcurrent flow through the loop will be normal. If the loop current falls to zero, the current in the polarizing winding, although tending to operate relay 9, will not do so because, unaided, it is not strong enough. If, however, the current supplied to the loop is reversed and approximately normal in amount, its eilect will aid that of the polarizing winding and the differential relay 9 will operate. The closing of its contact will operate relay 10 which will reverse the connections of the loop circuit. In doing this, it is pointed out that it will momentarily open the loop circuit, but this will not cause the differential relay 9 to release because the current in the polarizing winding is strong enough to hold it in the operated position. If, after operation of the loop with reversed current, the current should fall to zero, the differential relay 9 will not release for the same reason; but, if after operation of the loop with reversed current, the current should be made to flow in the normal direction and in approximately normal amount, the eifect of the difi'erential winding will beneutralized sutficiently to allow the ditlerential relay 9 to release. This will release relay 10 and restore the loop to its normal polarity.

. In Fig.2 is shown a modification of the arrangements of Fig. 1. In Fig. 2 certain parts of the telegraph repeater apparatus well known in the art and shown heretofore in Fig. 1 have been omitted. The loop circuit may be traced as follows: conductor 11, con tact of jack 12, conductor 13, contacts of relay 20, conductor 22, apparatus 14 in the subscribers station, conductor 23, contacts of relay 20, conductor 19, contact of jack 15 to battery 18. The relay 20 is a diilerential relay having one winding bridged across conductors 13 and 19. The relay 20 has another winding which acts as a polarizing winding .in connection with battery 21. The operat ing, holding and releasing values of relay 20 are similar to those of relay 9 ofFig. 1. It will be seen that if the current in the loop circuit is reversed from normal, the relay will operate and by means of its contacts will transfer the loop circuit connections so that the current flow through apparatus in the loop at the subscribers station will be in the normal direction.

In Fig. 3 is shown a modification of the arrangements of Figs. 1 and 2 in that the relay 20 is provided with two sets of make-beforebreak contacts. These will short-circuit the 2 loop during operation, maintaining current through the relay winding and avoiding the necessity of a second relay.

In Fig. 4 1s shown-a further modification of the arrangements of the invention. In

this arrangement, the winding of relay 20 is shunted by a rectifier 31 in series with a resistance 30. V A rectifier of the copper oxide contact variety may be utilized in this connection if desired. When current flow in the loop circuit is in such direction that the rectifier interposes but little resistance, only a slight current will flow through the operat ing winding of the relay 20. The effect of the holding winding, which is in circuit with battery 21, is in opposition to this. The current through the holding winding by itself must not be strong enough to operate the relay 20. When current flows through the loop in the opposite direction, the rectifier 31 will oppose its flow and all of the current will go through the operating winding and will operate the relay. If this current should fall to zero, the current in the holding winding is strong enough to keep the relay operated. If the current reverses to the first mentioned direction, the resistance 30 in series with the rectifier will cause some current to be shunted through the operating winding, sufiicient in amount to neutralize the effect of the holding winding and thereby allowing the relay to release. It will be seen that changes in the polarity of the current in the loop will cause the operation of relay 20 to reverse the connections of the loop circuit to apparatus at the subscribers station.

In a further modification of the arrangements of the invention illustrated in Fig. 5, two polar relays 20 and 20 are shown con nected in series across the loop circuit. These polar relays are adjusted so that they will remain on either contact when no current is flowing in the windings. A reversal of current flow in the loop will effect these relays to cause a reversal of the connections of conductors 22 and 23, so that the direction of current flow through apparatus 14 will remain normal. 7

While the invention has been disclosed as embodied in certain specific arrangements which are deemed desirable, it is understood that it is capable of embodiment in many and other widely varied forms without departing from the spirit of the invention as defined by the appended claims.

What is claimed is:

1. A telegraph line terminating at a'central ofiice, a loop circuit for extending said line to apparatus at a subscribers station, and means at said central ofli'ce responsive to a changein the direction of current flow in said loop circuit for reversing the connections of said loop circuit at said central office. r

2. A telegraph line terminating at a central office, a loop circuit for extending said line to apparatus at a subscribers station, and relay means at said central oflice respon sive to a change in thepolarity of current flow in'said loop circuit for reverslng the manner in which the apparatus at the sub scribers station is connected into said loop circuit.

3. A telegraph line terminating at a central oflice, a loop circuit for extending said trolled by said relay for reversing the connecline, a relay at said central ofiice having a tions of said 100p circuit. line Winding associated with said 100p circuit In testimony whereof, I have signed my 10 and a holding winding in a separate circuit, name to this specification this 21st day of 5 said windings being arranged to have oppos May, 1928. V 7 ing effects when the loop current is of a definite pclarity, and switching means con- JAMES A. EYSTER. 

